I would use a very long string and a big shell for the first shot and still worry shooting light loads. A very lite load of fast powder should reduce the pressure at the 10 inch mark. Something like 7625 might be still building pressure at the 10 inch mark. A good barrel man could turn out to be very cheap.
bill
Question about "still building pressure at the 10 inch mark": Seems everything I've read indicates that max pressure is always reached inside the chamber (with both black and smokeless powder), after which there's a gradual decline. Some powders lose pressure quicker than others, but I don't recall any instance of pressure still building at the 10" mark. Were that true, wouldn't our barrel walls need to be as thick at that point as they are in the chambers?
